Batteries become safe to swallow with spongy covering

Eating a battery may no longer require a trip to the emergency room.

With squishy silicone and tunneling electrons, researchers have created coated batteries that prevent unwanted zaps. The quantum-inspired coating works by switching from being a conductor —which it is when squeezed into an electronic gadget’s battery housing —to an insulator when it’s taken out and, perhaps, accidentally gulped.